Air pollution is a serious health issue throughout the world. More than
100 million people in Latin America reside in areas where air pollution
exceeds limits set by the World Health Organization. Air pollution in
Mexico City and Sao Paulo has been linked to deaths in adults and children,
respiratory problems in children (such as asthma), emergency room visits,
and other problems (Bell, 2006). Sixteen of the world's most polluted
cities are in China. One third of the country suffers from acid rain,
the area around Bejing suffers the worst levels of nitrogen dioxide in
the world, and China is second to the U.S. as a producer of greenhouse
gases. More than 100 million Chinese reside in areas in which the air
pollution can reach levels considered to be very dangerous and air pollution
is implicated in more than 400,000 premature deaths per year. There are
days in which a quarter of the particulate pollution of Los Angeles originated
in China (Watts, 2005). In Europe, air pollution causes twice as many
premature deaths as do car accidents (Blatt, 2005).
Air pollution is implicated in sixty thousand deaths per year in the United
States. Six percent of Americans have asthma. In the United States, hospital
admissions for respiratory problems such as asthma increased during periods
of high levels of ozone and sulfur dioxide pollution (Wilson, 2005). Diabetics
with a history of heart disease are at a special risk for adverse health
effects caused by air pollution (Goldberg, 2006). Children and the elderly
are also at high risk for the effects of air pollution. In the U.S. and
other industrialized countries, asthma incidence is rising. Between 1979-1991,
asthma rates rose 56% for Americans under 18 and children under 4 were
the fastest growing group entering the hospital for asthma attacks.
Air pollutants are detoxified in humans by a number of enzymes, including
glutathione-S-transferases (GSTs). Deletions of GST genes are relatively
common in humans (half of Caucasians suffer a deletion of GSTM1 and 15-20%
lack GSTT1). The genetics of GST deletions seem to interact with environmental
factors (such as exposure to cigarette smoke) to make the development
of childhood asthma more likely (Kabesch, 2006).
--after Kemp, 2004
SULFUR, NITROGEN, AND ACID RAIN
Is this rain acidic?
Sulfur and nitrogen oxides are respiratory irritants that affect breathing,
lower resistance to respiratory infections, and aggravate asthma and emphysema.
Nitrogen oxides (nitric oxide NO and nitrogen dioxide N2O form in automobile
engines which are not only irritants themselves but react with other molecules
to form the components of photochemical smog. Sulfur is a component of
coal which produces sulfur dioxide when burned.
The levels of sulfur and nitrogen oxides can reach critical levels in
the air. A number of northern Chinese cities have 3-8x the World Health
Organization limits for sulfur dioxide. The West German Ruhr region had
sulfurous smoke in 1/85 and 2/87 that caused schools to close. The use
of private cars was prohibited, there were advisories to stay indoors
(especially the young & old), and industry & power stations were
told to reduce emissions 30% or shut down. During the Czech winter 1989-90,
there were 7 episodes in which bronchitis & lung infections of newborns
increased 50% (American Chemical Society, 1994).
During the period of 1980-2000, sulfur emissions decreased 37% in the
U.S. and 56% in Europe but increased 250% in Asia. The World Bank estimates
that China loses $5 billion per year due to the effects of acid rain (Speth,
Sulfur and nitrogen oxides in themselves are not only dangerous, they
can produce acid when mixed with water.
4 NO2 + 2 H2O + O2------------' 4 HNO3 (nitric acid)
2 SO2 + O2 ------------------------' 2 SO3
SO3 + H2O---------------'H2SO4 (sulfuric acid)
The acids produced in the atmosphere lead to acid rain, acid snow, and
acid fog. The most tragic incident related to this was a deadly fog over
London in 1952 which caused 4000 deaths. A similar fog in Donora, Pa.
in 1948 caused 20 deaths. Thanks to better pollution standards, deadly
fogs are a thing of the past (American Chemical Society, 1994).
Water molecules (H2O) can dissociate into H+ and OH- ions. Pure water
is neither acidic nor basic since there is a balance between these two
ion concentrations. Other compounds can also produce these ions-acids
produce H+ ions (as in hydrochloric acid HCl below) and many bases produce
OH- ions (such as sodium hydroxide NaOH below).
How many H+ ions exist can make the difference between life and death.
The pH scale is a scale to measure the concentration of H+; water is neutral
(since [H+] = [OH-]) and represents a pH of 7. Acids have a higher concentration
of H+ and have pH values of 0-6.9. The lower the pH, the stronger the
acid. Bases remove H+ from solution and have pH values of 7.1-14. The
higher the pH the stronger the base.
While normal rainwater has a pH between 5.3-6.0 (this is slightly acidic
due to carbon dioxide dissolving in water to form carbonic acid), the
average rainfall of much of the northeast NE U.S. is pH 4.5. Some fogs
of Southern California have registered pH 2.5 and 1.5. Scotland had a
rainstorm of pH 2.4; central China has had rainstorms and streams of pH
EFFECTS OF ACID RAIN:
National Academy of Sciences estimates that acid rain causes $6 billion
a year in damages in the U.S.
--It erodes limestone and marble, rusts iron, and causes the deterioration
--It aggravates respiratory illnesses such as asthma and emphysema.
--It dissolves heavy metals in underwater sediments and dissolves lead
from water pipes into drinking water. At pH 6.3 water dissolves .03 µg
Pb (lead)/g water; at pH 4.4 it dissolves .8 µg; at pH 2.4 it dissolves
--Lower pH water kills fish. Healthy lakes have pHs of about 6.5. At a
pH 5.5 many fish disappear and at pH 5.0 most aquatic life disappears.
A lake with a pH of 4.0 is essentially dead. Most of the lakes of Scandinavia
are dead due to acid rain. In the Northeastern United States, the damage
of acid rain on the fishing industry was estimated to fall between $5.3
and 27.5 milllion. Acid rain in Norway may cost the fishing industry 1
million dollars (Mentz, 2004). Not only is the annual pH of rainwater
important, but so is the occurrence of episodic acid rain events. Such
events have been shown to effect the wetlands of the Northeastern U.S
--Acid leaches nutrients from soil and changes the populations of soil
organisms. This slows rates of organic decay and changes plant species
that can survive in the soil. There has been massive tree deterioration
and death in Germany & Eastern Europe; many U.S. forests also suffer.
As soil pH drops, plants suffer periodic aluminum toxicity. If the soil
pH drops to 3.0-4.2 loss of biomass and the loss of certain species. In
soils under pH 3.5, only plants with root systems restricted to the top
soil layer can survive. In the Northeastern U.S. and Canada, there is
evidence of acid rain damaging forests, such as those composed of sugar
maple and higher altitude red spruce (Mentz, 2004).
-- Acid rain can negatively effect the distribution of wildlife, such
as the wood thrush (Hames, 2002).
In 1980 several northeastern states and Canada sued the EPA to take
stronger measures against acid rain (Mentz, 2004). In 1980, the Acid Precipitation
Act led to the formation of the National Acid Precipitation Assessment
Program (NAPAP). Its 1998 report warned of adverse effects due to prolonged
acid rain over multiple decades (Mentz, 2004). Under the Clean Air Act
of 1990, sulfur dioxide levels were to be capped at 8.9 million tons by
the year 2000. The Clean Skies Initiative would cap sulfur dioxide at
4.5 million tons by 2010 and nitrogen oxide production to 2.1 million
tons by 2008 (Mentz, 2004).
Acid rain remains a problem in the Northeastern United States, in Europe,
and in Southeast Asia. Chinese coal consumption is the second greatest
in the world and Chinese coal possesses high amounts of sulfur. The resulting
acid rain affects much of China and even Japan and Korea. Some cities
have annual pH levels of 3. The amount of China which was affected by
acid rain increased from under 11% in 1985 to about 25% in 1993 (Terada,
OTHER AIR POLLUTANTS
There are other air pollutants which people are exposed to. These pollutants
are especially a problem for those who live in cities, whether the city
is Asuncion, Paraguay, Rio de Janeiro, or New York City.
OZONE, THE POLLUTANT
While atmospheric ozone is required for life on earth, it is potentially
harmful when it is breathed. At low altitudes, it is a pollutant. Even
low concentrations of ozone can decrease lung function in healthy people
and it worsens asthma. Maximum hourly concentrations of .05 ppm may cause
headaches, concentrations of .15 ppm cause eye irritation, and concentrations
of .29 cause coughs and chest discomfort. In L.A. 9/79, there were 10
consecutive days in which ozone concentrations exceded .35 ppm. Hospital
admittance of emphysema and asthma patients increased up to 50%. Ozone
levels in Mexico City are a serious problem for much of the year. Low
altitude ozone also damages plants and is estimated to cause $3 billion
in damage in the U.S. Ozone is blamed in part for the dieback of forests
in Mexico, Israel, and parts of Europe.
CO (carbon monoxide) causes more deaths in U.S. than any other gas. The
hemoglobin in red blood cells binds carbon monoxide 210 times as well
as it binds oxygen. When 70-80% of a person's hemoglobin have bound CO,
death results. Chronic sublethal exposure to carbon monoxide may lead
to brain damage and mental changes. When fossil fuels undergo combustion
without sufficient oxygen, carbon monoxide is produced. Several hours
in air that is 1 ppm (part per million) carbon monoxide can cause death;
the amount produced in heavy traffic can result in headaches, drowsiness,
& blurred vision. Industry, cars, fossil fuel burning, and slash and
burn agriculture produce 1500 tetragrams of carbon monoxide (1012 grams)/
In 1975, the catalytic converter was added to cars to reduce the amount
of carbon monoxide produced by the combustion of gasoline. Although the
number of cars in America doubled between 1970 and 1990, carbon monoxide
emissions dropped by almost 40% (American Chemical Society, 1994).
Particulates are small pieces of solid materials dispersed into the atmosphere.
When Kuwait's oil wells were set afire during the Persian Gulf War, an
estimated 4 million barrels of oil (whose sulfur content was 2.5%) burned
per day producing 20,000-40,000 tons of sulfur dioxide & 100,000 tons
of sooty smoke. The decrease in temperature caused by the soot was estimated
to be 4-10oC. Particulate pollution has been a problem in the past. In
Europe & North America in the 1930s-40s, many urban areas received
less than 50% of their potential winter sunshine. It was not uncommon
for Pittsburgh & London to require streetlights during the day. Some
particulate pollution raises additional health concerns. Asbestos (from
brake linings & insulation), for example, can cause cancer.
Increased levels of particulate air pollution, even when these levels
are below the EPA accepted limits, are correlated with an increased number
of patients with congestive heart failure admitted to hospitals in the
U.S. cities. The elderly, diabetics, and patients with a history of heart
disease were more likely to be affected (Wellenius, 2006). The emissions
of carbon particulates and sulfur dioxide from coal has increased more
than 6 times in South Asia since 1930. These pollutants have resulted
in the formation of atmospheric brown clouds which have cooled surface
temperatures and reduced rainfall amounts. The frequency of drought and
other adverse climate changes in South Asia may increase as these emissions
increase (Ramanathan, 2005). Particulate air pollution causes some of
its adverse health effects through oxidative damage to DNA (Risom, 2005).
Higher levels of particulate air pollution increase the risk of heart
attack, ventricular arrhythmias, artery acute vasoconstriction, and the
number of hospital emissions for cardiovascular disease (Peters, 2001;
Rich, 2005; Brook, 2002).
Because of human activity and air pollution, cities are usually warmer
than the surrounding non-urban areas. In the U.S., this urban heat-island
effect is usually just over one degree Celsius but it is almost 3 degrees
Celsius for New York City. In other parts of the world, this effect causes
an increase of more than 3 degrees in Moscow and occasional increases
of 6.5 degrees Celsius in China (IPCC, 1990).
INDOOR AIR POLLUTION
For many individuals, the greatest sources of air pollution they experience
occur inside the home (Zhao, 2005). Cigarette smoke is a significant source
of pollution and there are more than 4,000 chemicals present in cigarette
smoke. Other sources of indoor air pollution include the outgassing which
occurs from a variety of household items such as carpet to plastics and
the allergens which contribute to asthma ranging from pet dander to dust
While there are problems with air pollution today, many problems of the
past have already been largely solved. Many areas have much cleaner air
than they once did.
Tetraethyl lead, when added to gasoline, prevents premature explosion
(knocking) but unfortunately, it is also a neurotoxin, and its release
can affect brain development in children. Since 1976, all new cars and
trucks in U.S. run on unleaded on unleaded gasoline and annual lead emissions
have dropped dramatically. Unfortunately, unleaded gasoline is a little
more expensive than leaded gasoline and some developing nations still
use leaded gasoline. Leaded gas is still used in Mexico City, where 85%
childhood diseases are blamed on air pollution and 32 tons of lead emissions
are released per day. Although the U.S. banned tetraethyl lead since 1975,
this country still ships it to other countries (American Chemical Society,
1994). Two thirds of the gasoline in China still contains lead (Blatt,
2005). In the photo below of a gas station in Paraguay, note the distinction
between the most widely used regular gas which contains lead ("comun")
and the super unleaded gas ("super sin plomo").
Clean Air Acts and regulation of pollution have had a major impact on
air quality. For example, Pittsburgh's air has greatly improved in the
past decades, most Nashville residents don't know city was once called
"Smoky Joe", and London's present problems are nothing like
the "killer smogs" of the 1950s. Sulfur dioxide, CO, lead, and
particulate concentrations have decreased since 1975. Before the British
Alkali Act of 1863, bronchitis had been nicknamed the "British Disease".
The Clean Air Act was made law under Nixon and was strengthened under
George H. Bush. The EPA concluded that for the time period up to 1990,
"an additional 205,000 Americans would have died prematurely and
millions more would have suffered illnesses ranging from mild respiratory
symptoms to heart disease, chronic bronchitis, asthma attacks, and other
severe respiratory problems.". The EPA concluded that the strengthening
of the act under George H. Bush could prevent "23,000 premature deaths,
and avert over 1.7 million incidents of asthma attacks 67,000 incidents
of chronic and acute bronchitis 4.1 million lost work days"
per year in the future. (Union of Concerned Scientists, 2004)